Volcano Live

Isabela Island, Galapagos Islands, Ecuador

0.83 S, 91.17 W
summit elevation 1124 m
shield volcano

Sierra Negra volcano is located on the southern end of Isabela Island, Galapagos Islands.

The volcano contains a 7 x 10 km wide caldera. There are numerous cinder cones, spatter cones, and tuff cones.

Sierra Negra volcano is the largest on Isabela Island, but has a low profile of less than 5 degrees. A large eruption in 1979 produced a 14 km high ash cloud and lava flows which reached the sea.

2005 Eruption
Sierra Negra volcano erupted on the Galapagos Islands on 22nd October 2005 at 2330 hr UT. Ash was observed to 25,000 ft. The eruption was preceded by seismic activity felt at the village Villamil 20 km SE of the caldera. At At 1730 hr an explosion was heard by people in the village. Lava fountains occurred to a height of 300 m, with eruption occurring along a 2-km fissure near the caldera's N rim.

On 23rd October 2005 lava flowed from the crater at a speed of 20 metres per second. Lava flowed for a distance of 800 m in channels up to 50 m wide. The volume of the lava erupted by 1530 hr on 23 October was calculated at about 25 million cubic meters. The eruption ended on the 30th October 2005. Lava from the eruption covered about 14 sq km of the caldera floor (0.05 cubic km). This was much less than the eruption in 1979 which erupted 1 cubic km of lava.

1979 Eruption
The entire northern flank was covered by lava erupted from a circumferential fissure in the 1979 eruption.

Further reading
Reynolds, R.W., Geist, D. and Kurz, M.D., 1995. Physical volcanology and structural development of Sierra Negra volcano, Isabela island, Galápagos archipelago. Geological Society of America Bulletin, 107(12), pp.1398-1410.

Reynolds, R.W. and Geist, D.J., 1995. Petrology of lavas from sierra negra volcano, isabela island, galápagos archipelago. Journal of Geophysical Research: Solid Earth, 100(B12), pp.24537-24553.